what is?

Depending on where you've heard ABC from, but to me it stands for "Amercian Born Chinese". It is a term we use for any Chinese that was born in North America. There is also a term called "Chinese born Canadian" which is CBC, that's me. If you are from an asian country, the term ABC will usually come up and considered to be cool. But, the term FOB wouldn't be that good "Fresh Off the Boat" meaning refugees and new chinese immagrants. Sorry, I went a little bit off topic.

There are some islands in the Caribbean which are known by the acronym "The ABC Islands"

The American Broadcasting Company (ABC) is a television and radio network in the United States. at least thats the only ABC im aware of.